Aminothiazole-aromatic amides of formula I
wherein Ar is aryl or heteroaryl, L is an optional alkylene linker, and R2, R3, R4, and R5, are as defined in the specification herein, are useful as kinase inhibitors, in particular, inhibitors of protein tyrosine kinase and p38 kinase. They are expected to be useful in the treatment of protein tyrosine kinase-associated disorders such as immunologic and oncological disorders [see, U.S. Pat. No. 6,596,746 (the '746 patent), assigned to the present assignee and incorporated herein by reference], and p38 kinase-associated conditions such as inflammatory and immune conditions, as described in U.S. patent application Ser. No. 10/773,790, filed Feb. 6, 2004, claiming priority to U.S. Provisional application Ser. No. 60/445,410, filed Feb. 6, 2003 (hereinafter the '410 application), both of which are also assigned to the present assignee and incorporated herein by reference.
The compound of formula (IV), ′N-(2-Chloro-6-methylphenyl)-2-[[6-[4-(2-hydroxyethyl)-1-piperazinyl]-2-methyl-4-pyrimidinyl]amino]-5-thiazolecarboxamide, is an inhibitor of SRC/ABL and is useful in the treatment of oncological diseases.

Other approaches to preparing 2-aminothiazole-5-carboxamides are described in the '746 patent and in the '410 application. The '746 patent describes a process involving treatment of chlorothiazole with n-BuLi followed by reaction with phenyl isocyanates to give chlorothiazole-benzamides, which are further elaborated to aminothiazole-benzamide final products after protection, chloro-to-amino substitution, and deprotection, e.g.,

The '410 application describes a multi-step process involving first, converting N-unsubstituted aminothiazole carboxylic acid methyl or ethyl esters to bromothiazole carboxylic acid esters via diazotization with tert-butyl nitrite and subsequent CuBr2 treatment, e.g.,
then, hydrolyzing the resulting bromothiazole esters to the corresponding carboxylic acids and converting the acids to the corresponding acyl chlorides, e.g.,
then finally, coupling the acyl chlorides with anilines to afford bromothiazole-benzamide intermediates which were further elaborated to aminothiazole-benzamide final products, e.g.,

Other approaches for making 2-aminothiazole-5-carboxamides include coupling of 2-aminothiazole-5-carboxylic acids with amines using various coupling conditions such as DCC [Roberts et al, J. Med. Chem. (1972), 15, at p. 1310], and DPPA [Marsham et al., J. Med. Chem. (1991), 34, at p. 1594)].
The above methods present drawbacks with respect to the production of side products, the use of expensive coupling reagents, less than desirable yields, and the need for multiple reaction steps to achieve the 2-aminothiazole-5-carboxamide compounds.
Reaction of N,N-dimethyl-N′-(aminothiocarbonyl)-formamidines with α-haloketones and esters to give 5-carbonyl-2-aminothiazoles has been reported. See Lin, Y. et al, J. Heterocycl. Chem. (1979), 16, at 1377; Hartmann, H. et al, J. Chem. Soc. Perkin Trans. (2000), 1, at 4316; Noack, A. et al; Tetrahedron (2002), 58, at 2137; Noack, A.; et al. Angew. Chem. (2001), 113, at 3097; and Kantlehner, W. et al., J. Prakt. Chem./Chem.-Ztg. (1996), 338, at 403. Reaction of β-ethoxy acrylates and thioureas to prepare 2-aminothiazole-5-carboxylates also has been reported. See Zhao, R., et al., Tetrahedron Lett. (2001), 42, at 2101. However, electrophilic bromination of acrylanilide and crotonanilide has been known to undergo both aromatic bromination and addition to the α,β-unsaturated carbon-carbon double bonds. See Autenrieth, Chem. Ber. (1905), 38, at 2550; Eremeev et al., Chem. Heterocycl. Compd. Engl. Transl. (1984), 20, at 1102.
New and efficient processes for preparing 2-aminothiazole-5-carboxamides are desired.